Alexander Zverev

He's sitting at #2 with 9,690 points, and that's also his career high — he's never been #1. Fresh off winning the US Open, so the momentum is real. The honest answer is I can't tell you the exact gap to whoever's ahead without that number in front of me, but at #2 with a Slam just banked, he's about as close as it gets. I'd say the chances are genuinely good if he keeps this form through the indoor swing, though it'll come down to how the guy above him defends his points.